1. Field of the Invention
The present invention relates generally to a simulation system for an automotive prime mover, such as an internal combustion engine, for testing automotive components, such as an automatic or manual power transmission. More specifically, the present invention relates to a simulation system for an automotive internal combustion engine which provides an output characteristic equivalent to that of the automotive engine.
2. Description of the Background Art
Japanese Patent First Publications (Tokkai) Nos. 58-38833 and 61-53541 each disclose a bench testing system for an automatic power transmission. In the disclosed system, an electric motor or a hydrostatic motor with a speed increasing device is used in place of an automotive internal combustion engine.
As appreciated, since the electric motor or the hydrostatic motor has a much larger inertia in comparison with the automotive engine, it is practically difficult to control the operation of those motors, even combined with the speed increasing device, to simulate the transitional characteristic of the automotive engine at the shift of a transmission speed ratio. For example, the electric motor has a inertial magnitude about 10 times greater than that of the automotive engine.
Accordingly, in general, the automotive engine simulation systems employing such motors are only useful for testing durability, steady-state characteristic, and so forth, of the power transmission, but not for testing the transitional characteristic of the power transmission at the speed ratio shifting.
However, for designing an automatic power transmission with an improved shift feeling, reduced shift shock and so forth, it is essential to obtain data of the transitional characteristic of the automatic power transmission.
In order to improve the automotive engine simulation system employing the electric motor, the above-noted Japanese Patent First Publication No. 61-53541 performs correction of a command current for the electric motor to compensate for a differential in inertia between the electric motor and the automotive engine, so as to provide a simulated transitional torque characteristic similar to that of the automotive engine. However, in this background art, a substantial delay is caused in controlling the command current, which is not suitable for specifically testing the transitional characteristic of the power transmission since the high-speed response is required for testing same. Accordingly, in this background art, it is difficult to obtain the transitional characteristic data of the power transmission equivalent to those derived by using the automotive engine.